Update to timely 0.19 #525

Job	Run time
test mdBook	1m 21s
cargo test on ubuntu, rust stable	42s
cargo test on ubuntu, rust 1.78	53s
cargo test on macos, rust stable	57s
cargo test on macos, rust 1.78	1m 3s
cargo test on windows, rust stable	3m 2s
cargo test on windows, rust 1.78	1m 48s
	9m 46s

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